In many ways, the sophisticated motion of organisms is enabled by the selective stiffening of soft tissue. Cephalopods rely on muscular hydrostats for structural support and locomotion without a skeletal system. Land based organisms also use hydrostatic mechanisms for selective stiffening of tissue (e.g., the trunk of an elephant or the spongy tissue of the corpora cavernosa).
The field of soft robotics endeavors to use compliant structures to reduce the complexity of machines while also increasing their sophistication towards that of biological analogs. One manifestation of this goal is embodied intelligence: instead of a central computer that commands multiple components in a prescribed way, distributed networks of materials automatically respond to their environment. An example of embodied intelligence in nature is that of a tree's leaves collapsing in a strong wind to prevent its branches from breaking. Soft elastomers that can deform at very low stresses (˜100's of kPa's) can program embodied intelligence into pneumatically actuated machines; a prime example is that of an “open-loop” gripper that wraps around objects based on their difference in stiffness. Another outcome of using easily deformable materials and structures in soft robotics is smooth and continuous motions during actuation—mobile robots move in similar fashion to biological organisms, with simple machine design. While these motions are similar, their functional mechanisms are completely different (i.e., muscle fibers vs. inflating members).
Thus, there is a need for soft actuators made of a construction that enables formation into any geometry and of a construction that facilitates controlled movement of the actuator. The soft actuators are made from materials that can be manipulated, for example to simulate selective stiffening. The invention satisfies this need.